1. Field of the Invention
The present invention relates to a semiconductor device including an insulating interlayer composed of a low-dielectric-constant insulating material, and method of manufacturing the same.
2. Description of the Related Art
With recent demands on faster operation speed of semiconductor devices, a great deal of investigational efforts have been made on alteration of an insulating interlayer from conventional silicon oxide film (dielectric constant K=4.3 or around) to a low-dielectric-constant insulating material layer, in order to reduce the inter-wiring capacitance. The low-dielectric-constant insulating material referred to herein is any insulating material having a dielectric constant of 3.6 or below. Examples of the low-dielectric-constant insulating material include HSQ, carbon-containing silicon oxide material and aromatic-group-containing organic resin material those having a dielectric constant of 3 or around. In pursuit of further reduction in the dielectric constant, recent developmental efforts are also made on a porous material having micro-pores introduced into the film. Use of this sort of low-dielectric-constant insulating material to the insulating interlayer makes it possible to reduce inter-wiring crosstalk, and to realize fast operations of elements.
Use of the low-dielectric-constant insulating material as the insulating interlayer, however, raised a problem of showing a poor adhesiveness to an etching stopper film or a protective film such as SiCN film or the like, and of causing peeling-off.
Japanese Laid-Open Patent Publication No. 2002-203899 discloses a technique of plasma treatment improving the adhesiveness of the insulating layer for the case where copper is used as a wiring material.
The conventional method is, however, raised a problem in that the plasma treatment must be respectively given to copper and barrier metal layer in order to ensure a desirable adhesiveness, and this makes the process complicated.
The above-described degradation in the adhesiveness between the insulating interlayer and the etching stopper film or the like is likely to occur particularly for the case where the insulating interlayer contains carbon in the lower layers of the multi-layered wiring film. FIG. 6 is a chart showing results of adhesiveness between an SiOC film, formed as an insulating interlayer by the CVD process, and a SiCN film, evaluated under varied C (carbon) content of the SiOC film. The evaluation of the adhesiveness herein was made by the m-ELT (modified edge liftoff test) process. As is known from the chart, the adhesiveness decreases as the carbon content of the SiOC film increases.
It is therefore supposed that lowering in the carbon content of the insulating interlayer may improve the adhesiveness between the insulating interlayer and the etching stopper film or the like. The lowering in the carbon content of the insulating interlayer, however, raises a new problem of increase in dielectric constant of the film.